diff --git a/src/convert.jl b/src/convert.jl
index 57778f925..f70d755e7 100644
--- a/src/convert.jl
+++ b/src/convert.jl
@@ -1,4 +1,4 @@
-(::Type{SA})(x::Tuple) where {SA <: StaticArray} = error("No precise constructor for $SA found. Length of input was $(length(x)).")
+(::Type{SA})(x::Tuple{Tuple{Tuple{<:Tuple}}}) where {SA <: StaticArray} = error("No precise constructor for $SA found. Length of input was $(length(x)).")
 
 @inline (::Type{SA})(x...) where {SA <: StaticArray} = SA(x)
 @inline (::Type{SA})(a::AbstractArray) where {SA <: StaticArray} = convert(SA, a) # Is this a good idea?
diff --git a/test/custom_types.jl b/test/custom_types.jl
new file mode 100644
index 000000000..251779a5a
--- /dev/null
+++ b/test/custom_types.jl
@@ -0,0 +1,7 @@
+@testset "Custom types" begin
+    # Issue 123
+    @eval (struct MyType{N, T} <: StaticVector{T}
+        data::NTuple{N, T}
+    end)
+    @test (MyType(3, 4) isa MyType{2, Int})
+end
diff --git a/test/runtests.jl b/test/runtests.jl
index 34c28cdfc..addd19c38 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -10,6 +10,7 @@ using Base.Test
     include("MArray.jl")
     include("FieldVector.jl")
     include("Scalar.jl")
+    include("custom_types.jl")
 
     include("core.jl")
     include("abstractarray.jl")